This invention relates to novel crosslinked block copolymers composed of a polycarbosilane portion consisting mainly of units of the formula --Si--CH.sub.2 -- and a polymetallosiloxane portion consisting of units of the formula --M--O-- in which M is Ti or Zr and units of the formula --Si--O--, and to a process for production thereof.
It is known that polycarbosilane, a polymer having a main chain skeleton composed of --Si--CH.sub.2 -- with two side-chain groups bonded to each silicon atom, is converted to an inorganic carbide SiC on firing, and therefore SiC fibers having good mechanical and thermal properties can be produced by molding polycarbosilane into fibers and firing the resulting fibers. The present inventors disclosed this technique in U.S. Pat. No. 4,100,233.
The present inventors also disclosed in U.S. patent application Ser. No. 953,518 filed Oct. 23, 1978 that polycarbosilane whose main chain skeleton is composed mainly of --Si--CH.sub.2 -- and contains a minor proportion of --Si--O-- is an especially good material for production of SiC fibers.
The present inventors assiduously furthered their investigations on organometallic polymers, and have now found novel copolymers composed of a polycarbosilane portion and a polymetallosiloxane portion which are bonded to each other by crosslinking. They have found that these novel copolymers are very useful because composite inorganic carbide fibers having better properties than SiC fibers obtained from conventional polycarbosilane can be produced by molding such a copolymer into fibers and firing the resulting fibers.